(1) Technical Field
The invention relates to a material handling container of the type for packaging, shipping, and inventorying goods. More specifically, the invention relates to a reusable, molded thermoplastic container which is collapsible when empty and stackable in either the collapsed or upright position in order to reduce the space required to ship or inventory goods stored in the container.
(2) Description Of The Prior Art
Material handling containers used for packaging, shipping and inventorying goods are well known in the art. For example, U.S. Pat. No. 4,591,065 issued to Foy on Mar. 27, 1986; U.S. Pat. No. 4,917,255 issued to Foy et al. on Apr. 17, 1990; U.S. Pat. No. 4,923,079 issued to Foy; U.S. Pat. No. 4,674,647 issued to Gynge et al. on Jun. 23, 1987; U.S. Pat. No. 4,775,068 issued to Reiland et al. on Oct. 4, 1988; and U.S. Pat. No. 5,094,356 issued to Miller on Mar. 10, 1992 all disclose collapsible containers having a base and four walls which are hingedly connected to the base. The walls are moveable between a collapsed position where the walls are folded one on top of the other and an upright position where the walls extend vertically upward from the base to define an interior of the container.
Containers of the type disclosed in the patents listed above are made of plastic and are generally the largest of their class having dimensions ranging from approximately 40-45 inches in width, .times. approximately 48 inches in length, .times. approximately 25-39 inches in height. Typically, in the prior art, each wall and base of such containers are molded separately using a structural foam molding process. The structural foam molding process is often employed to mold large parts such as those which make up a collapsible container. This is a low pressure molding process in which a gas foaming agent, typically nitrogen, is introduced upstream of the mold foam material, typically high density polyethylene plastic. The foaming agent aids the material to spread out and fill the entire mold until the mold is fully packed. The gas foaming agent defuses out of the material leaving a porous part having a cellular structure.
However, there are certain disadvantages attendant with structural foam plastic molded containers. For example, the minimum wall thickness required when using structural foam is 0.250 inches. Further, large parts such as walls and bases need to be reinforced with strengthening ribs. As a result, structural foam containers have thick heavy walls and bases producing an overall container weight of between 150 and 170 pounds.
The greater the thickness of a base or wall, the longer it takes for the part to cool in the mold. This increases mold cycle time which is a critical variable in the manufacturing process. The longer the cycle time, the fewer parts that can be made per hour. As such, longer cycle times increase the cost of each container. In addition to increased costs due to weight and cycle time, structural foaming also reduces the material properties such as impact resistance and tensile strength.
Accordingly, there is a need for a light-weight, thin walled, strong material handling container which can be molded in shorter cycle time using less material and therefore reducing the cost of the container.
The subject invention overcomes all of these deficiencies in the prior art and meets the above-identified needs in a cost effective, durable, light-weight, thin walled, reinforced thermoplastic material handling container which can be molded in shorter cycle times without a loss in material properties of the container.